title: A novel, noninvasive transdermal fluid sampling methodology: IGF-I measurement following exercise.
abstract: This study tested the hypothesis that transdermal fluid (TDF) provides a more sensitive and accurate measure of exercise-induced increases in insulin-like growth factor-I (IGF-I) than serum, and that these increases are detectable proximal, but not distal, to the exercising muscle. A novel, noninvasive methodology was used to collect TDF, followed by sampling of total IGF-I (tIGF-I) and free IGF-I (fIGF-I) in TDF and serum following an acute bout of exercise. Experiment 1: eight men (23 ± 3 yrs, 79 ± 7 kg) underwent two conditions (resting and 60 min of cycling exercise at 60% Vo(2)(peak)) in which serum and forearm TDF were collected for comparison. There were no significant changes in tIGF-I or fIGF-I in TDF obtained from the forearm or from serum following exercise (P > 0.05); however, the proportion of fIGF-I to tIGF-I in TDF was approximately fourfold greater than that of serum (P ≤ 0.05). These data suggest that changes in TDF IGF-I are not evident when TDF is sampled distal from the working tissue. To determine whether exercise-induced increases in local IGF-I could be detected when TDF was sampled directly over the active muscle group, we performed a second experiment. Experiment 2: fourteen subjects (22 ± 4 yr, 68 ± 11 kg) underwent an acute plyometric exercise condition consisting of 10 sets of 10 plyometric jumps with 2-min rest between sets. We observed a significant increase in TDF tIGF-I following exercise (P ≤ 0.05) but no change in serum tIGF-I (P > 0.05). Overall, these data suggest that TDF may provide a noninvasive means of monitoring acute exercise-induced changes in local IGF-I when sampled in proximity to exercising muscles. Moreover, our finding that the proportion of free to tIGF-I was greater in TDF than in serum suggests that changes in local IGF-I may be captured more readily using this system.
authors.affiliation: Military Performance Division, United States Army Research Institute of Environmental Medicine, Natick, MA 01760, USA.
authors.forename: D E
authors.initials: DE
authors.lastname: Scofield
authors.forename: H L
authors.initials: HL
authors.lastname: McClung
authors.forename: J P
authors.initials: JP
authors.lastname: McClung
authors.forename: W J
authors.initials: WJ
authors.lastname: Kraemer
authors.forename: K R
authors.initials: KR
authors.lastname: Rarick
authors.forename: J R
authors.initials: JR
authors.lastname: Pierce
authors.forename: G J
authors.initials: GJ
authors.lastname: Cloutier
authors.forename: R A
authors.initials: RA
authors.lastname: Fielding
authors.forename: R W
authors.initials: RW
authors.lastname: Matheny
authors.forename: A J
authors.initials: AJ
authors.lastname: Young
authors.forename: B C
authors.initials: BC
authors.lastname: Nindl
mesh_terms: D000293:Adolescent; D000328:Adult; D001642:Bicycling; D015444:Exercise / Q000502:physiology*; D005260:Female; D005542:Forearm; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007834:Lasers; D008297:Male; D012146:Rest / Q000502:physiology; D012867:Skin / Q000378:metabolism*; D013048:Specimen Handling / Q000295:instrumentation / Q000379:methods*; D014619:Vacuum Curettage; D055815:Young Adult
chemical_list: D007334:Insulin-Like Growth Factor I